Pex gets eaten through by rats and then you get to replace 20% of your house if you don't catch it in time. Copper for water is better, or you could run PEX in CSST conduit everywhere (never seen or heard of it). I don't know enough about rats and CPVC, but it seems a bit safer at least. But you will get rats, it's just a question of when.
Why doesn't anyone run PEX in CSST conduit (flexible galvanized steel, for those who don't know, as is commonly used to protect wiring) if this is such a problem? Flexible conduit is a hell of a lot cheaper than copper pipe, easier to bend and connect too.
It looks good as well. At the same time, all these plastic materials are petroleum based products we are piping our drinking water through, although we likely have no choice for this century at least.
